The present invention relates to a processing apparatus, more specifically to a processing apparatus with a collimator exchange device for sputtering articles on objects to be processed.
A semiconductor device fabrication process conventionally uses a sputtering system to form electrodes on objects to be processed, such as semiconductor wafers and to wire the objects. The sputtering system is positioned opposed to a target of a required film forming material in a processing chamber, the interior of which is kept in a required low pressure atmosphere, whereby sputtering particles sputtered from the target are applied to the objects.
Accompanying the recent high integration of semiconductor devices, techniques for accurate micronized processing in their fabrication processes are required to be established. In internal wiring processing by sputtering systems, for example, it is necessary to bury contact holes having small diameters and large depths, i.e., high aspect ratios, with sputtering particles. But generally the sputtering processes have low step coverage characteristics, and as the cavities of the contact holes have larger aspect ratios, wiring breakage tends to take place at the bottom of the holes. This is a problem for the conventional technology.
As a countermeasure to this problem, recently a sputtering system including a collimator 5 which comprises, as shown in FIGS. 11 and 12, a plurality of circular through-holes 5a or a honeycomb of through-holes 5a formed through a metal plate of, e.g., steel or an insulating plate of ceramics has been used. The collimator 5 is positioned between a target and objects to be processed to restrict directions of radiation of sputtering particles in a cos .THETA. distribution from the target to select components which will substantially perpendicularly bombard the surfaces of the objects to be processed, whereby improved step coverage is obtained. By the use of such collimator, step coverage is improved by about three times the usual step coverage for contact holes of aspect ratios of above 3.0 which are required in fabrication of, e.g., 64 MB DRAMs.
But the use of a collimator in a sputtering system for improved step coverage extremely lowers film forming speeds of forming films on an object to be processed because most of sputtering particles are trapped by the collimator or are adhered to the collimator in films. For example, it is known that when the processing is conducted by applying the same electric power to a sputtering system with a collimator and to a sputtering system without a collimator, a film forming speed of the former is lowered to a speed 1/3-1/20 that of the latter. Besides, a film forming speed further lowers depending on a period of time in which the collimator is used, and a film forming amount for the collimator. In addition, film forming materials themselves trapped by the collimator peel into particles, and the collimator installed in the processing apparatus has to be periodically replaced for the prevention of generation of particles.
But in the conventional sputtering system, when the collimator is replaced, the interior of the processing vessel is released from a vacuum into the atmospheric air every time the collimator is replaced. The operation to this end is complicated and takes time. This has been a serious barrier to improvement of throughputs of the processing apparatus.